1. Field of the Invention
The present invention relates to an anodic bonding structure, a fabricating method thereof, and a method of manufacturing an optical scanner using the same, and more particularly, to an anodic bonding structure of a dielectric and a glass substrate or a dielectric and a metal layer, a fabricating method thereof, and a method of manufacturing an optical scanner using the same.
2. Description of the Related Art
Anodic bonding is a technique of bonding a silicon substrate widely used in the fabrication of a micro sensor device and a glass substrate having a thermal expansion coefficient similar to that of a silicon substrate. Pyrex glass, i.e., Corning glass 7740, generally used in an anodic bonding process includes predetermined amounts of sodium (Na) and potassium (K) so that when the Pyrex glass is heated at a temperature of over 200° C., elements are charged and easily moved by a voltage. When a silicon substrate and a glass substrate are aligned and a voltage of over 600 V is applied to the substrates, movable charges move rapidly. Thus, strong dielectric charges occur on the interfaces of the silicon substrate and the glass substrate to bond the silicon substrate with the glass substrate. A plurality of micro-electromechanical systems (MEMS) processes use an anodic bonding method that realizes a stable silicon structure.
FIG. 1 is a sectional view of a conventional anodic bonding structure. A conventional anodic bonding structure is formed of a substrate 13 placed on a base plate 11 and a glass substrate 15 installed above the substrate 13. When the structure is heated at the above-described temperature, and a cathode and an anode are connected to an upper portion of the glass substrate 15 and a lower portion of the base plate 11, respectively, to apply the above-described voltage, charged ions move between the substrate 13 and the glass substrate 15 to perform a strong anodic bonding.
An anodic bonding process may be used in a method of manufacturing an optical scanner. In a conventional method of manufacturing an optical scanner, only thin silicon substrates are used, thereby an automation process is difficult. Also, a torsion bar is driven in an unstable manner and is easily broken, and the yield is lowered. Although a silicon substrate and a glass substrates are bonded to obtain a stable device, it is impossible to obtain the perfect torsion bar. Therefore, a silicon on insulator (SOI) substrate has been used to stably realize a bonding structure; however, an electrical isolation problem within the SOI substrate occurs.